An endoscope apparatus is known that includes a function for determining the concentration of a biological substance (e.g., hemoglobin) in biological tissue that is the imaging subject, based on color information in an endoscopic image. An example of this type of endoscope apparatus is disclosed in WO 2014/192781 (called “Patent Document 1” hereinafter).
The endoscope apparatus disclosed in Patent Document 1 is an endoscope apparatus that, based on color information in two endoscopic images captured using illumination light in two types of wavelength regions in hemoglobin's absorption band at roughly 550 nm, calculates an indicator that indicates the total hemoglobin amount and an indicator that indicates the degree of oxygen saturation SatO2.